It is too frequently observed that disk brakes of automobiles or other mechanical installations, upon brake pedal release, disengage or retract from a braking position without complete clearance of contact. The result is that the brake pad remains in a loose "scraping" position, which drag continuously increases the needless consumption of fuel or energy. This condition is sometimes attributed to the aging of O-ring seals of the brake piston assembly, plus corrosion of contacting metal which may freeze the piston seal. However study will show that there is really no reliable structure provided in current brake assemblies which will positively and completely retract the operating piston after each release of fluid pressure.
It seems to be expected that since the brake fluid is in a closed hydraulic system, the relief of fluid pressure will automatically move the piston back. However, too often this is not the situation. Accordingly it is an object now to provide such a positive action, self-aligning piston retraction construction which can be installed as original equipment on various mechanisms, particularly on brakes of motor vehicles, or which can be fitted as a reconstruction unit in presently unsatisfactory brake assemblies. This can be done with a minimum of modification, specifically by reducing the piston circumference to provide a retaining recess for the control unit which is then attached to the surrounding slot which previously held a ring seal.